drm/vc4: Add missing formats to vc4_format_mod_supported().

Daniel's format_mod_supported() patch predated Dave's for NV21/61, and
I didn't catch that when rebasing.  This is a problem since the
formats are now getting validated before being passed to the driver's
atomic hooks.

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Daniel Stone <daniels@collabora.com>
Cc: Dave Stevenson <dave.stevenson@raspberrypi.org>
Fixes: 423ad7b ("drm/vc4: Advertise supported modifiers for planes")
Link: https://patchwork.freedesktop.org/patch/msgid/20180316220435.31416-2-eric@anholt.net

drivers/gpu/drm/vc4/vc4_plane.c

@@ -873,7 +873,9 @@ static bool vc4_format_mod_supported(struct drm_plane *plane,
 	case DRM_FORMAT_YUV420:
 	case DRM_FORMAT_YVU420:
 	case DRM_FORMAT_NV12:
+	case DRM_FORMAT_NV21:
 	case DRM_FORMAT_NV16:
+	case DRM_FORMAT_NV61:
 	default:
 		return (modifier == DRM_FORMAT_MOD_LINEAR);
 	}